For in-process transportation of a wafer in a processing step of a thin plate-form workpiece such as a silicon wafer, for example, it is usual to use a box or a cassette having plural of slots to store one wafer per each. The transported box or cassette is set to a processing apparatus in a step at the destination, and the wafers are taken out therefrom and are set to the processing apparatus. The wafers subjected to the processing are stored to a box or a cassette again, and transported to the next step.
On this occasion, the transportation of wafers, in which wafers are taken out from a box or a cassette, set to a processing apparatus, and stored to a box or a cassette, are performed automatically by a robot or an actuator, etc. without handwork in many cases.
In such transportation of wafers, wafers are held by a hand attached to a robot or an actuator (hereinafter, also referred to as a workpiece holding apparatus), transported to the destination, and released thereto (see Patent Document 1). In this case, it is usual to adopt a method such as aspirating suction, an edge grip, a Bernoulli chuck for holding the wafers.
Herein, a workpiece holding apparatus using aspirating suction will be described with referring to FIGS. 10 (a) and (b).
The workpiece holding apparatus 101 is provided with an air controlling mechanism 106 and a vent 103. This is configured to aspirate air in suction of a workpiece W, and is configured to stop this aspiration when separating (detaching) the workpiece W or to supply air in order to enhance the separation.
In the workpiece holding apparatus 101 using this aspirating suction, the workpiece holding portion is usually pasted with a suction pad 104 having elasticity. This suction pad 104 sucks the workpiece W by aspirating air through an opening 105. In this case, it is possible to enhance the aspiration effect by increasing the adhesiveness between the workpiece W and the holding portion by the suction pad 104. It is also possible to prevent an occurrence of a defect on a workpiece due to direct contact between the main body 102 of the holding apparatus and a workpiece W.